Fiducial markers in prostate for kV imaging: quantification of visibility and optimization of imaging conditions
Fiducial markers in prostate for kV imaging: quantification of visibility and optimization of imaging conditions
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DOI：
10.1088/0031-9155/57/1/155
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发表时间：
2012-01-07
影响因子：
3.5
通讯作者：
McDonough, James E.
中科院分区：
文献类型：
--
作者：
Chen, Yu;O'Connell, John J.;McDonough, James E.
这项工作的目的是研究可植入前列腺的更小、密度更低的基准标记，以在质子龙门架上的机载 kV-kV 成像系统中进行目标定位和患者重新定位验证。实验使用了骨盆模型和各种市售基准标记：phi 的 CIVCO 碳标记； 1 x 3 mm，phi 金色种子标记； 0.8 x 3 毫米和 phi； 1.2 x 3 毫米和 IBA Visicoil 螺旋金色线性标记，直径为 0.35、0.50、0.75 和 1.15 毫米。布置了两个正交机载 kV 成像仪，用于通过横向和前后方向对体模进行数字放射成像。计算给定标记的对比度噪声比 (CNR)，并将其用作其可见性的定量测量。测量患者入口皮肤暴露 (ESE) 并参数化 kVp、mAs 和源到表面距离。首先引入 CNR 与 ESE 的比率来表征使用给定 X 射线技术对标记物进行成像的效率，以便优化标记物的可见度并同时最小化 X 射线成像剂量。如果 CNR > 2（对应于显着性 p < 0.05）才能获得可接受的可见度，则碳标记物和最小的 Visicoil 标记物不适合通过致密骨进行成像，但其他标记物能够在临床中使用。据预测，正在开发的其他标记物的厚度应大于 0.14 毫米厚的金，以便在横向 kV 成像中产生可接受的可见度。 phi 的线性 Visicoil 标记； 0.50 x 5 mm 最适合用于质子治疗的前列腺 kV 成像，因为它在可接受的标记物中引起的质子剂量扰动最小。使用最大 CNR/ESE 和 CNR > 2 确定 120-130 kVp 和 40-80 mAs 的最佳范围，以便对前列腺中的该标记物进行横向成像。
The purpose of this work is to investigate possible smaller, less-dense fiducial markers implantable into the prostate for target localization and patient repositioning verification in an on-board kV-kV imaging system on a proton gantry. The experiments used a pelvic phantom and a variety of commercially available fiducial markers: CIVCO carbon marker of phi; 1 x 3 mm, gold seed markers of phi; 0.8 x 3 mm and phi; 1.2 x 3 mm, and IBA Visicoil helical gold linear markers in diameters of 0.35, 0.50, 0.75 and 1.15 mm. Two orthogonal on-board kV imagers were arranged for digital radiographic imaging of the phantom through the lateral and anterior-posterior directions. The contrast-to-noise ratio (CNR) for a given marker was calculated and used as a quantitative measure of its visibility. The patient entrance skin exposure (ESE) was measured and parameterized for kVp, mAs and source-to-surface distance. The ratio of CNR to ESE was first introduced to characterize the efficiency for imaging a marker using a given x-ray technique in order to optimize the marker's visibility and simultaneously minimize the x-ray imaging dose. If CNR > 2, which corresponds to a significance p < 0.05, is required for acceptable visibility, the carbon marker and the smallest Visicoil marker are not suitable for imaging through dense bone but the others are capable of being employed in the clinic. It is predicted that other markers in development should have a greater thickness than equivalent of 0.14 mm thick gold in order to produce the acceptable visibility in the lateral kV imaging. The linear Visicoil marker of phi; 0.50 x 5 mm is most suitable for kV imaging in the prostate for proton therapy as it induces the least proton dose perturbation amongst the acceptable markers. An optimal range of 120-130 kVp and 40-80 mAs is determined using the maximal CNR/ESE and CNR > 2 for laterally imaging this marker in the prostate.